A Siren's Tail
by UltimateFangirlofFangirling
Summary: They were childhood friends, but one day, an event would take place; separating them for years. A killer in the water, a killer on the ground. What happens when both sides collide? (Picture credit goes to LeonS-7 on Deviant Art)
1. Chapter 1

It was a normal day in the kingdom of Fairy Tail. The sun seemed to glow on the vibrant activity. Townspeople went about their business, trading magical and non-magical items and striking up their own friendly conversations. Traders came in with large caravans, eager to sell their merchandise to all the happy citizens. To any observer, the kingdom of Fairy Tail was one of the most prosperous, and lively places in all of earthland. In all of the commotion, one cloaked figure ran through the streets unnoticed; his movement's swift and silent. Or, at least, he believed he was unnoticed.

After reaching the tree line, the boy stopped and lowered his hood. Pink hair glowed vibrantly under the sunlight for a few moments before he continued moving into the forest and its surrounding shade.

The figure moved among the trees, dodging them faster than any other child he knew, as he did take everything as a competition and would certainly never lose. When he finally reached a clearing he let out a loud whoop of joy. After jumping around with happiness for a few moments, the boy reached into his bag and brought out a small amulet, reflecting with pure crystal.

When the boy could suddenly hear splashing, he froze and a grin creeped across his face. Thoughts of childish revenge danced in his mind. He covered his head and creeped over a hill to stare at the occupants of a small pond.

A small girl could be seen splashing in the water; her face wearing a stunning smile. She was joined by an older woman, with long blue hair. The woman's face was filled with mild disgust as the little blonde girl splashed her with water. The patient observer gradually came out from his hiding spot and creeped behind the blonde girl, near the edge of the pond. A smirk came from the older woman as she had saw him approaching long ago and clearly approved of his devilish plan. The boy reached down and tickled the girl with all his power as he attempted to avoid the now deathly splashes.

The blonde's reaction changed from scared to surprised to amused.

"Natsu! If you wanted to join me, you could've just said!" She reached behind her and dragged the assailant into the water. After a few fits of coughing and laughing, the soaked boy pulled himself onto the bank and lay on his back, defeated by the small girl.

The older woman watching laughed at the scene, "You should've seen that coming, Natsu. You should know Lucy's never one to go down without a fight!"

The young boy laughed, but he felt a little annoyed that someone as small as her could turn his own trick against him. He decided the change the subject.

"Lushi! Lemme see your fins!" Lucy looked slightly appalled.

"One, my name is Lu-CY and two, it's called a tail, not fins!"

"Why, aren't you a fish?" The older woman moved between them before a fight could break out.

"Natsu, be careful of what you say to Lucy. She's a princess, you know."

"I'm a prince! Aquarius, she should be my wife!" There was a large sigh from the elder fin lady.

"I wish it was that simple. Now treat her with respect and," She turned to Lucy," you do the same for him. You're both royalty in your own kingdoms." Natsu looked a bit scolded before he perked up over his original question.

"Lucy, may I see your tail please?" The blonde's face dashed with a light blush at the boy's sudden change in tone.

"M-m-yeah, I guess." She swerved her body around and brought her tail out of the water. The scales were bright pink, and glittered in the sunlight. The water glossed over each scale in a rippling sheen.

Natsu found his mouth wide open.

"It's rude to stare at a lady, Natsu." Aquarius teased the small boy. Having being found out, the boy became very flustered and reached into his bag quickly.

"I-I-I got this for you." Natsu placed the shiny amulet on the bank and sprinted away. "See ya later, Lucy!" As he sprinted through the trees with a happy grin on his face, he was unaware that this short meeting would be the last he would see of his friend in a very, very long time.


	2. Chapter 2

14 years later.

Natsu looked out the window at his kingdom with boredom. He could see children running on the streets and people conversing happily with each other. His thoughts strayed to when he used to roam through the kingdom, free, unrestrained, and without burden. Any observer that had seen Natsu's face at that moment would have confessed that his expression looked like one of pain, confusion, and loss. It was a small knock on his bedchamber door brought him to his senses, and wiped his face of emotion.

"Come in." A petite girl walked in, carrying a small pile of clothes. Her light blue hair seemed to lighten the room and cheer up the atmosphere. The faint smell of books trailed behind her.

"Natsu, I brought your newest wardrobe for this special occasion." She grinned and nearly skipped over to the young king.

"Thanks! Can you send the ice pop up to me?"

"Of course, your-"

"I'm not one for formalities, Levy" The pink-haired king gave a toothy grin that was enough for any girl to fall for him. The blunette blushed and ran out of the room. After she left, the king's facade dropped and he began to get dressed; a chore, he might add, that he still did without the help of any servants.

After he removed his shirt, he stopped and stared at himself in the mirror. A cross shaped scar covered a large portion of his abdomen. He looked a few moments longer before rushing to clothe himself again as if nothing had happened. The garments he would be wearing today were the most rich and lavish garments he had ever worn, but there was no surprise to why.

Natsu sighed, before setting his crown purposefully lopsided on his head. This little act of rebellion was one of the few things that brightened his day. That and…

"Oi flame-brain!" Well speak of the devil.

"Hey, ice pop." The new voice belonged to an armor-clad soldier. He walked over and punched Natsu in the chest.

"Don't look so down. It's your birthday after all."

"Whoop de fucking doo." The comment earned him another rough hit.

"Watch your mouth!" Natsu threw a punch back.

The fight began to escalate quickly as more punches were thrown and assorted vases and mirrors were smashed mercilessly. After the two boys had worn themselves out, they both wore bright grins. Natsu couldn't think of a better way to start the day off.

"See ya at the celebration, Gray." The king righted his clothing and walked out of his bedchamber.

"That idiot left me with this mess to clean up? Ridiculous."

Natsu walked alone towards the throne room. As he passed his court members, he would give a curt nod to his soldiers or a small smile to the palace maids. The castle was unusually busy as many people across the kingdom had come to celebrate his birthday. His attention was drawn when a beautiful girl with long white hair walked to meet him. She had a tall blonde man on her arm. They both held themselves like royalty.

"Your majesty." The woman curtsied and her escort bowed. "My name is Mirajane, and this is my husband, Laxus. We are just a few of your new lords and ladies."

"New lords and ladies? What happened to the previous ones?" The look on Lady Mira's face clearly told Natsu that he had asked the wrong question.

"They turned treasonous, your majesty, and fled to a nearby kingdom."

"When did this happen?"

"Over the past few years, your court has left you. Are you telling me you haven't noticed?"

Natsu felt ashamed. It was indeed his court, but he had not payed attention to anything in the past five years. Not since his father had passed, anyway.

"My dealings in the castle haven't been too involved. I trust Lord Dreyar to handle the state of the court." Laxus' eyes widened. He spoke for the first time in a dark tone.

"I had no idea that my father had such a powerful influence on the kingdom."

"Lord Dreyar is your father?"

"Indeed, but he-"

"He arranged our marriage." Mirajane's cheerful tone cut off her husband's serious one. "We were against it in the beginning, but we truly fell in love with each other after a few months."

"Well, congratulations." Natsu found any further conversation to be awkward, so he bowed his head and walked past the couple.

Why had his court abandoned him? Had he really been so absent from the kingdom that this managed to slip by him? He wondered what else he had missed in his detached state. A memory flowed to the front of his mind.

 _It had been three weeks since his father's passing. Natsu had kept to his room for the entirety of his mourning, locking everyone else out. The sheets and pillows on his bed were ravaged, as if an angry animal had destroyed its prey. The pictures in the rooms had been burned, along with the wallpaper, and pieces of glass were littered across the floor._

 _A small hand knocked on the door. Silence. Another knock. Silence._

" _N-N-Natsu?" Silence. "Natsu, I'd just like to say that I'm sorry about you, l-l-loosing your father." Natsu sat quietly and listened to this girl's voice outside his door. She sounded so frail, and so familiar, but a stranger all the same._

 _Natsu usually would have yelled for the visitor to leave at this point, as he had done when Levy, Gray, and Erza had come to see him, but he couldn't force himself to yell at this girl. She sounded just as lost as he did._

" _I'm sorry." Muffled crying came from the other side of the door, and gradually dissipated as the visitor slowly left._

 _He never found out who the visitor was._

The amount of time Natsu had spent grieving could not be counted, as he was still grieving to this day. Igneel, king of Fairy Tail had been murdered five years ago, and the killer was never found. The body had been discovered lying in the river; a stab wound in the chest and his throat, cleanly cut. What the king had been doing outside the castle that night was unknown, as his body had been laden with traveling supplies when they found him. Natsu even wondered if his father had tried to abandon him that night, but he shook the thought off immediately, as he knew his father was the kindest king and father in the entire world.

Ever since that day, that so very dark and lonely day, Natsu had swore revenge against the murderer, and that he would use everything he had to track him down, even if it took the rest of his life. Following that promise, the young king began searching secretly in taverns, at balls, during hunting parties. However, apparently he had become complacent in other areas.

"Your Majesty! Master Makarov would like to see you!" The young king nearly rolled his eyes. He had a very good idea why his master was looking for him on this day in particular.

Natsu had hurried down a corridor and began descending a long flight of stairs into darkness. The castle itself had been incredibly busy with the preparation of his birthday celebration, but this part of the palace was silent and cold. As Natsu neared the bottom, he began to remove his excessive garments. When he finally stepped off the last stair, he was only wearing a pair of baggy pants. A large sword suddenly came swinging towards him and the king dodged it easily. He did not, however, dodge the incoming scolding.

"Natsu Dragneel, why didn't you come see as soon as you woke up?!" Natsu winced a little at his master's harsh voice.

"I was on my way, I just got held up a bit." He dodged another swing.

"Got held up? What if you had lost control?! What if you had hurt someone?!" Natsu had never hurt a soul in his life and hearing the suggestion was preposterous. He had even managed to have an entire brawl with Gray this morning without losing control.

"Chill out gramps, I'm fine."

"I will test that." A tiny old man hobbled out of the darkness. The old man carried a sword twice his height and double his width. However, disregarding his enormous weapon, the little man looked very weak and aged to a unfamiliar eye. Natsu knew not to underestimate him.

The room was suddenly filled with the sounds of battle as the pink-haired king fought the only person he trusted his secret to. Makarov threw more sword swings and Natsu continued dodging by running up walls and flipping through the air, disturbing the ancient dust from the empty dungeon.

The match appeared normal until Natsu suddenly lit his fists on fire. The battle swiftly changed from sword versus man to sword versus element. The pink-haired king stopped dodging and began blocking the attacks. Every block brought bright sparks into the room. Natsu advanced, blocking every blow and nearing his master. A swing from above gave the young king his chance, as he quickly and inhumanly dodged to the side, flipped over the blade and landed with his hands on the hilt of his master's sword. It clattered to the ground a second later.

A cheeky smile lit up his face as the king did a little victory dance.

"I got you gramps!" The old man scowled.

"This is by no means proof that you are safe today during your celebration. I really hope you see this as serious as it is, Natsu." The comment made Natsu a little irritated.

"Gramps, why do you think I'll lose control some day? It's never happened before! Haven't I proven myself?" The look on his master's face made him take a step back. He hadn't lost control before, had he? Pain was etched on the old man's face.

"Just take my words to heart and enjoy your celebration." He hobbled off into the darkness. Natsu winced and climbed out of the dungeon slowly, retrieving his fancy garments. His master's reaction had given him the answer he needed, but he couldn't remember ever losing control. Had it happened when he was too young to remember? The thoughts swirled in his mind as he finally righted his crown and exited the staircase.

The pink-haired king had taken two steps before he ran straight into someone, knocking them on the floor. He looked down in surprise to see a blonde girl wearing simple clothes. She seemed dazed until she saw Natsu standing in front of her. The girl quickly scrambled to her feet and bowed in front of Natsu so he couldn't see her face.

"I'm so sorry, your majesty. I should have been watching more closely." Natsu could see that she was quivering. He placed both hands on her shoulders and forced her to stand until their eyes met. A bright blue amulet around her neck caught the king's attention.

"Who are you?" The blonde fumbled to answer.

"L-L-Lucy Heartfilia, your majes-"

"Natsu, call me Natsu. I haven't seen you before, are you one of the servants?"

"No, I'm the court's physician." Natsu recognized her, but he couldn't remember from where. The amulet was also incredibly familiar to him.

"Do I know you?" The question made Lucy's eyes widen in surprise. She took a step away from the king.

"No, I don't believe we have met before. I was only appointed this year." Natsu opened his mouth to speak again, but Lucy began to leave. "I'm sorry, your majesty, I have some important business to attend to."

Before Natsu could respond or stop her, she had flitted around the corner and out of sight. The young king ran around the corner, but Lucy was gone.


End file.
